1. Field of the Invention
This invention relates, generally, to water craft. More particularly, it relates to a water craft design that incorporates a rigid concavity in the hull to reduce drag.
2. Description of the Prior Art
An inflatable dinghy is a small boat used to transport passengers from a larger boat to shore and back again. They have utility whenever the draft of the larger boat exceeds the depth of the water adjacent a wharf, pier, or shore.
A dinghy is made by a pair of generally parallel, elongate air-filled tubes that are interconnected at their respective forward ends by a transversely disposed air-filled tube that forms a bow. The parallel tubes form the sidewalls of the craft. A rigid transom to which a small outboard motor is secured interconnects the respective trailing ends of the sidewalls to one another. The deck of the dinghy is a piece of plastic or other suitable flat material that is connected about its periphery to the underside of the bow and the sidewalls. The deck is usually reinforced by a plurality of transversely disposed braces.
The floorboard of a dinghy overlies the deck and is formed of a rigid material such as plywood, aluminum, or the like. The floorboard may also be formed of an inflatable material.
A convex hull is positioned below the deck, and a longitudinally disposed rib is typically provided as a part of the hull to maintain the convex shape of the hull.
The outboard motor typically used with a dinghy has about five (5) horsepower and the top speed of a dinghy is usually about eight (8) knots.
A dinghy cannot be made to travel significantly faster by increasing the horsepower of its motor or the thrust provided by its propeller. Due to its flexible construction, the deck begins to fold along transversely disposed lines if more power is applied to its stern. In other words, a dinghy shortens in the direction of travel if it is thrust forward with enhanced power. The folded bottom wall greatly increases the resistance to forward travel.
There are times when the distance from an anchored boat to shore is quite long. Thus, the trip in the dinghy can consume substantial amounts of time. It would be beneficial, then, if a dinghy could be modified so that it could travel at a much faster rate than the current eight (8) knots.
There are many other types of small craft, such as dinghies that are made of rigid, non-inflated materials, RIBs (rigid inflatable boats), motorboats, single-hulled sailboats, catamarans, trimarans, rowboats, canoes, and so on. The realm of small craft could also be expanded to include floatable items such as surfboards and windsurfing boards.
Accordingly, if a way could be found to improve the performance of a typical inflated dinghy, then the same technology could be applied to all other small craft.
The same technology could be applied to large craft as well.
Moreover, any technology employed for the purpose of enabling a water craft to attain higher speed when under its own power also has the beneficial side effect of reducing drag when a small craft is towed by a larger craft.
Since reduction of drag translates into increase of speed, a means for reducing the drag in a water craft is desirable.
Earlier inventions in this field of technology are disclosed in U.S. Pat. No. 3,742,888 to co-inventor Crowley, as well as in U.S. Pat. Nos. 3,688,724, 3,518,956, and Great Britain patent No. 1,001,059.
However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the known water crafts could be modified to further reduce drag and increase speed.